<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <div class="form-item">
      <input type="text" required id="userName" />
      <span class="bar"></span>
      <label for="userName"> User Name</label>
    </div>
  </body>
  <style>
    * {
      margin: 0;
      padding: 0;
    }

    html,
    body {
      width: 100%;
      height: 100%;
      position: relative;
    }

    .form-item {
      width: 300px;
      height: 40px;
      position: absolute;
      top: 50%;
      left: 50%;
      transform: translate(-50%, -50%);
      border-bottom: 1px solid #898989;
    }

    input {
      width: 100%;
      height: 100%;
      border: none;
      outline: none;
    }

    .bar {
      display: block;
      margin: 0 auto;
      width: 0;
      height: 2px;
      background-color: #5264ae;
      transition: 0.4s ease;
    }

    label {
      font-size: 26px;
      position: absolute;
      top: -7px;
      left: 0;
      transition: 0.4s ease;
    }

    .form-item input:focus ~ .bar {
      width: 100%;
    }

    .form-item input:valid ~ label {
      color: #5264ae;
      transform: translateY(-30px);
    }

    .form-item input:focus ~ label {
      color: #5264ae;
      transform: translateY(-30px);
    }
  </style>
</html>
